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From: Linus Torvalds <torvalds@linux-foundation.org>
Date: Mon, 3 Jun 2024 09:57:42 -0700
Message-ID: <CAHk-=wha2rH2UcTvHUYK+dNnP6UCDRkYM0atvw_GTP5Sz3OZrQ@mail.gmail.com>
Subject: Re: [PATCH 00/14] alpha: cleanups for 6.10
To: "Maciej W. Rozycki" <macro@orcam.me.uk>
Cc: "Paul E. McKenney" <paulmck@kernel.org>, 
	John Paul Adrian Glaubitz <glaubitz@physik.fu-berlin.de>, Arnd Bergmann <arnd@kernel.org>, 
	linux-alpha@vger.kernel.org, Arnd Bergmann <arnd@arndb.de>, 
	Richard Henderson <richard.henderson@linaro.org>, Ivan Kokshaysky <ink@jurassic.park.msu.ru>, 
	Matt Turner <mattst88@gmail.com>, Alexander Viro <viro@zeniv.linux.org.uk>, 
	Marc Zyngier <maz@kernel.org>, linux-kernel@vger.kernel.org, 
	Michael Cree <mcree@orcon.net.nz>, Frank Scheiner <frank.scheiner@web.de>
Content-Type: text/plain; charset="UTF-8"

On Mon, 3 Jun 2024 at 04:09, Maciej W. Rozycki <macro@orcam.me.uk> wrote:
>
>  Anyway, back to my point.  A feasible solution non-intrusive for Linux
> and low-overhead for GCC has been found.  I can expedite implementation
> and I'll see if I can regression-test it too, but I may have to rely on
> other people to complete it after all, as I haven't been prepared for this
> effort in the light of certain issues I have recently suffered from in my
> lab.

Yeah, if compiler support makes us not have to care, then I don't
think the difference between pre-BWX and BWX is going to matter much
for the kernel.

The real pain with alpha has been that it's special enough that it
affects non-alpha code, and BWX was one big piece of that.

That said, some of the EV4 misfeatures end up being a huge pain inside
the alpha code either because of the horrible hoops that the IO
accessors have to jump through, or because of the broken ASID's.

So even with enw compiler support, maybe it's worth trying to
re-introduce any support for older cpu's incrementally.

For example, the ASID hw issue is _claimed_ to have been fixed in
PALcode, and maybe the games we played for ev4-era cpus aren't
actually needed any more?

And the various odd IO platforms should only be re-introduced when
there are people who actually have access to the relevant hardware and
will test.

           Linus